Administrators and staff is the likely answer. From 1975 to 2005 there was no change in faculty-to-student ratios, but students per administrator dropped from 84 to 68 (and pay increased) and students per professional staffer dropped from 50 to 21. Source: http://www.amazon.com/The-Fall-Faculty-Benjamin-Ginsberg/dp/...

Someone already did: http://www.amazon.com/The-Fall-Faculty-Benjamin-Ginsberg/dp/...